Shift work and medically certified sickness absence due to common mental disorders among nursing staff: a prospective cohort study.

Sickness absence due to common mental disorders is rising among healthcare staff, yet evidence on the impact of shift work remains inconsistent. This study examined the association between shift work and the risk of first-time medically certified sickness absence (>14 days) due to common mental disorders (CMDs) among nursing staff. This 11-year prospective cohort study included 25 120 nurses and nursing assistants employed for one year or more between 2008 and 2019 in Region Stockholm. Shift work data were obtained from an employee register, and CMD-related sickness absence (N = 2792) from the Swedish Social Insurance Agency, for the study period 2009-2020. Discrete-time proportional hazards models estimated hazard ratios, adjusted for demographic factors and profession. Shift work was assessed in the year preceding sickness absence. Lower hazard ratios (HRs) for sickness absence due to CMDs were found among shift workers with night shifts (HR 0.80, 95% CI 0.72-0.89) and among permanent night workers (HR 0.81, 95% CI 0.65-0.99), compared with day workers. Frequent night shifts (>121/year) were associated with a lower risk (HR 0.77, 95% CI 0.65-0.90) compared with non-night workers. Among non-night workers, frequent quick returns (>49/year) from afternoon shifts (defined as less than 11 hours between shifts) were associated with a lower HR (HR 0.72, 95% CI 0.56-0.92) compared with never having quick returns. Shift work among nursing staff was associated with a lower risk of sickness absence due to common mental disorders. This finding may reflect a selection of healthy individuals for night-shift work.